H-3609: Reduce cost of polling for notification and draft entities counts

[CiaranMn]

🌟 What is the purpose of this PR?

We display a count of (a) notifications and (b) draft entities requiring processing in the top navigation bar and sidebar.

The data for this is currently fetched by an app-wide context which polls for notifications and draft entities. This fetches all the notification and draft entities, because it is also used by the notifications and draft queue pages, which require the actual entity data.

App-wide we only need the count of entities, not the entities themselves. This PR therefore splits those contexts out into (1) app-wide contexts for fetching the count only, and (2) contexts used in the relevant pages only, which gets the rest of the data.

This reduces the amount of data we are polling for while not on the notifications or draft queue pages.

Pre-Merge Checklist 🚀

🚢 Has this modified a publishable library?

This PR:

• does not modify any publishable blocks or libraries, or modifications do not need publishing

📜 Does this require a change to the docs?

The changes in this PR:

• are internal and do not require a docs change

🕸️ Does this require a change to the Turbo Graph?

The changes in this PR:

• do not affect the execution graph

🛡 What tests cover this?

• None yet.

❓ How to test this?

1. Not possible via the preview deployment as it relies on Node API changes.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 22.99%. Comparing base (3790335) to head (f423140).
Report is 8 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5838      +/-   ##
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- Coverage   22.99%   22.99%   -0.01%     
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  Files         569      569              
  Lines       19096    19094       -2     
  Branches     2709     2709              
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- Hits         4392     4390       -2     
  Misses      14652    14652              
  Partials       52       52              

Flag	Coverage Δ
apps.hash-ai-worker-ts	1.32% <ø> (ø)
apps.hash-api	1.16% <ø> (ø)
local.hash-backend-utils	8.80% <ø> (ø)
local.hash-isomorphic-utils	0.99% <ø> (ø)

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